jan 1, 800 BC - Upanishads are Written
Description:
"The eleven major Upanishads are written around 800 BCE, and these become fundamental texts of Hinduism. These introduce the ideas of reincarnation and karma, that those who are righteous in the current life will be reborn in a better life until they eventually reach Nirvana, or the holy bliss."- softschools.com
Most likely different sages wrote the Upanishads. hinduwebsite.com says, "There is no definite answer to this question. This problem is not confined to literature or scriptures of Hinduism only. One of the fascinating truths about Hindu culture is that since ancient times the scholars of India who composed the great works such as the epics, the Puranas, or the Sutras, did not believe in taking credit for their work."
Added to timeline:
Date:
jan 1, 800 BC
Now
~ 2827 years ago